ORA-00824 cannot set sga_target

SQL> startup 

ORA-00824: cannot set sga_target due to existing internal settings, see alert log for more information 

[oracle@10g pfile]$ pwd

/u01/oracle/admin/xscen/pfile

[oracle@10g pfile]$ ls

init.ora.2152011182431

[oracle@10g ~]$ sqlplus / as sysdba

SQL*Plus: Release 10.2.0.4.0 - Production on Mon Aug 27 16:19:10 2012

Copyright (c) 1982, 2007, Oracle.  All Rights Reserved.

Connected to an idle instance.

SQL> create spfile from pfile='/u01/oracle/admin/xscen/pfile/init.ora.2152011182431';

File created.

SQL> startup;

ORACLE instance started.

Fixed Size                  2083368 bytes

Variable Size              88081880 bytes

Database Buffers          188743680 bytes

Redo Buffers                6303744 bytes

Database mounted.

Database opened.

SQL> alter system set statistics_level=BASIC scope=spfile;

System altered.

SQL> alter system set sga_target=0 scope=spfile;

System altered.

SQL> shutdown immediate;

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL> startup;

ORACLE instance started.

Fixed Size                  2082496 bytes

Variable Size             113248576 bytes

Database Buffers           50331648 bytes

Redo Buffers                6303744 bytes

Database mounted.

Database opened.

SQL> 

SQL> show sga;

Fixed Size                  2083368 bytes

Variable Size             159385048 bytes

Database Buffers          117440512 bytes

Redo Buffers                6303744 bytes

SQL> show parameter spfile;

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

spfile                               string      /u01/oracle/product/10.0.2/db_

                                                 1/dbs/spfilexscen.ora

SQL> show parameter sga_target;

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

sga_target                           big integer 272M

SQL> show parameter db_recovery_file_dest;

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

db_recovery_file_dest                string      +FLASHVG

db_recovery_file_dest_size           big integer 10G

SQL> show parameter recovery;

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

db_recovery_file_dest                string      +FLASHVG

db_recovery_file_dest_size           big integer 10G

recovery_parallelism                 integer     0

SQL> show parameter statistics_level

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

statistics_level                     string      TYPICAL

SQL> alter system set statistics_level=BASIC scope=spfile;

System altered.

SQL> shutdown immediate;

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL> startup;

ORA-00824: cannot set sga_target due to existing internal settings, see alert log for more information

SQL> create spfile from pfile='/u01/oracle/admin/xscen/pfile/init.ora.7272012173945';

File created.

SQL> startup;

ORACLE instance started.

Fixed Size                  2083368 bytes

Variable Size             159385048 bytes

Database Buffers          117440512 bytes

Redo Buffers                6303744 bytes

Database mounted.

Database opened.

SQL> create pfile='//u01/oracle/admin/xscen/pfile/init.ora.20120828' from spfile;

File created.

SQL> alter system set statistics_level=BASIC scope=spfile;

System altered.

SQL> alter system set sga_target=0 scope=spfile;

System altered.

SQL> shutdown;   

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL> startup;

SQL> create spfile from pfile='/u01/oracle/admin/xscen/pfile/init.ora.7272012173945';

File created.

SQL> startup;

ORACLE instance started.

Fixed Size                  2083368 bytes

Variable Size             159385048 bytes

Database Buffers          117440512 bytes

Redo Buffers                6303744 bytes

Database mounted.

Database opened.

SQL> alter system set shared_pool_size=0 scope=spfile;

System altered.

SQL> alter system set large_pool_size=0 scope=spfile;

System altered.

SQL> alter system set java_pool_size=0 scope=spfile;

System altered.

SQL> alter system set db_cache_size=0 scope=spfile;

System altered.

SQL> alter system set streams_pool_size=0 scope=spfile;

System altered.

SQL> shutdown 

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL> startup

ORACLE instance started.

Fixed Size                  2083368 bytes

Variable Size             163579352 bytes

Database Buffers          113246208 bytes

Redo Buffers                6303744 bytes

Database mounted.

Database opened.

SQL> show parameter statistics_level;

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

statistics_level                     string      TYPICAL

SQL> shutdown immediate;

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL> startup;

ORACLE instance started.

Fixed Size                  2083368 bytes

Variable Size             163579352 bytes

Database Buffers          113246208 bytes

Redo Buffers                6303744 bytes

Database mounted.

Database opened.